The invention concerns an inductance arrangement or the construction of inductors, chokes and transformers with a very high power density.
Chokes are usual examples of inductance arrangements. Such a choke comprises a magnetic circuit and an electrical circuit, the latter usually comprising a copper winding. Depending on the respective area of use involved the magnetic circuit comprises laminated dynamo plates at lower and medium frequencies, while at higher frequencies it comprises for example ferrite.
Such a choke usually comprises two magnetically conductive limbs which are each enclosed by a respective copper winding and which are magnetically coupled together by yokes, wherein depending on the respective situation of use involved an air gap can be provided between a limb and a yoke. In this respect the inductance of such a choke can be calculated as follows:
(Equation 1)   L  =                    A        Fe                    I        Fe              ⁢          μ      0        ⁢          μ      e        ⁢          N      2      
wherein: AFe denotes the iron cross-section, IFe denotes the length of the iron path, N denotes the number of turns, xcexc0 denotes relative permeability and xcexce denotes effective permeability.
Magnetic induction accordingly can be calculated in accordance with the following formula:   B  =                    N        ·        I                    I        Fe              ⁢          μ      0        ⁢          μ      e      
Magnetic induction is the determining factor in regard to the design of inductive components or transformers. An increase in inductance of the induction B always also means a higher power density.
The iron losses PV,Fe within the magnetic circuit (core) are dependent in a wide range at low frequency in quadratic relationship on the inductance B. This is shown in FIG. 2. With even greater driving of the dynamo plate the iron losses rise very steeply, for which reason that range should generally be avoided. Conventional types of chokes however do not entail the possibility of dissipating high power losses as the iron limbs are insulated from the ambient atmosphere by the coil body, that is to say the copper winding. In this case there is practically no possible way of heat dissipation by radiation (winding over core) or heat dissipation by conduction (air gap). Therefore only a small amount of power loss can be removed from the magnetic circuit.
The object of the present invention is to improve the cooling of the magnetic circuit, to improve the efficiency of the induction arrangement described in the opening part of this specification and to markedly reduce the consumption of material for the windings so that with the same amount of power it is possible to achieve a lower weight and a reduced structural size for the induction arrangement.
In accordance with the invention it is proposed that individual plate packs in the induction arrangement are displaced relative to each other. That drastically increases the surface area at both sides of the iron core. That increase in the cooling area can be easily achieved, by a factor of between five and fifteen. Displacement of the plates of the limbs give rise to highly effective cooling passages or ducts between the core and the surrounding winding.
An increase in the induction B by about 10% also permits a number of turns which is 10% higher. That means however that the inductance increases by about 121% asxe2x80x94see formula 1xe2x80x94that increases in proportion to the square of the number of turns.
It is particularly effective if the mutually displaced plates or mutually displaced plate packs are oriented displaced through 90xc2x0 with respect to the longitudinal direction of a yoke. In that way the surface can be adjusted to a desired size by virtue of the displacement of the plates without in that case the winding of the adjacent magnetic circuits becoming closer.